Construct Binary Tree from Inorder and Postorder Traversal

后序与中序得原二叉树，与上篇类似。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        return build(inorder,postorder,inorder.size(),0,postorder.size()-1);
    }
    TreeNode* build(vector<int> &inorder,vector<int> &postorder,int size,int i,int p)
    {
        if(size==0)
        return NULL;
        TreeNode* head = (TreeNode*)malloc(sizeof(TreeNode));
        head->val = postorder[p];
        int j;
        for(j=i;j<i+size;j++)
        {
            if(postorder[p]==inorder[j])
            break;
        }
        head->left = build(inorder,postorder,j-i,i,p-size+(j-i));
        head->right = build(inorder,postorder,size-(j-i)-1,j+1,p-1);
        return head;
    }
};